##Your level 5 druid knows all of them on the Druid Spell list ...
... from levels 1, 2 and 3. 

The problem you have is: which ones does the druid prepare on a given day?  
###How to translate the rules?  
You have to make choices after each long rest to either (1) keep prepared the ones you had the day before or (2) prepare a different set.  This actually makes playing a druid and a cleric require a little more thought, and some forecasting, to try and have the right spells prepared for a given adventure. 

> Preparing and Casting Spells⁠  
> 
> **You prepare the list of druid Spells that are available for you to cast, > *choosing from the druid spell list*.**  
> 
> When you do so, choose a number of druid spells⁠ equal to your Wisdom
> modifier + your druid level (minimum of one spell). The spells⁠ must
> be of a level for which you have Spell Slots.

For example, if you are a 3rd-level druid, you have four 1st-level and two 2nd-level Spell Slots. With a Wisdom of 16, your list of prepared Spells can include six spells⁠ of 1st or 2nd level, in any combination. If you prepare the 1st-level spell Cure Wounds, you can cast it using a 1st-level or 2nd-level slot. Casting the spell doesn’t remove it from your list of prepared spells⁠.

You can also change your list of prepared Spells when you finish a Long Rest. Preparing a new list of druid spells⁠ requires time spent in prayer and meditation: at least 1 minute per Spell Level for each spell on your list.